1. Field of the Invention
The present invention relates to a frequency up-conversion system and method for the same, and, more particularly, to a frequency up-conversion system with an optical modulator and an optical phase shifter connected in parallel and a frequency up-conversion method for the same.
2. Description of Related Art
Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Current conventional network architectures using coaxial cable and twisted pair cable as the transmission medium cannot satisfy the users' requirement for high-speed transmission of data and high definition videos. Fiber-to-the-x (FTTx), based on the passive optical fibers, has been widely used in the wired high speed transmission services to provide transmission of voice, video and data. In addition, Radio over Fiber (RoF) is receiving increasing attention in research and development due to the rapidly increasing bandwidth needs of wireless communication.
FIG. 1 illustrates the conventional RoF architecture. As the bandwidth for wireless transmission increases, the carrier frequency increases accordingly. However, the transmission distance of the wireless microwave signal decreases as the carrier frequency increases. To solve this problem, the RoF technique uses the low loss property of the fiber transmission to effectively extend the service area of the wireless network, by loading the radio frequency signal onto the optical fiber for transmitting to the desired area, converting the radio frequency signal into the wireless high frequency signal using the optical-to-electrical converter, and transmitting the wireless high frequency signal to the user by the antenna, as shown in FIG. 1.
FIG. 2 illustrates the conventional hybrid access network architecture. Recently, there has been intensive research on the hybrid access network technique, which integrates the FTTx technique and the RoF technique. The hybrid access network technique effectively uses the existing optical fiber network to provide the transmission service for voice, video and data, so that the construction cost of the telecommunication entity on the wireless network can be dramatically decreased. However, the transmitting end needs an oscillation to generate the high frequency wireless signal carrier for high frequency transmission, and all the devices at the transmitting end must be able to work at such high frequency.
In the near future, the transmission rate will be increased to 10 Gbps in the high-definition multimedia interface (HDMI) 1.3. In response to this development, international companies including Intel, LG Electronics, Panasonic, NEC, Samsung, SiBEAM, SONY, and Toshiba have formed a WirelessHD Consortium to discuss the feasibility of using the 60 GHz carrier to transmit high-definition multimedia information. The 60 GHz carrier possesses the 7 GHz wideband characteristic and is very suitable for transmitting the high-definition multimedia information. However, to transmit data at this frequency band, all the devices at the transmitting end, including the oscillator, power amplifier, etc., need to operate at such high frequency, which dramatically increases the system complexity and construction cost.
The RoF technique can use the optical fiber with bandwidth of several tens of THz and very low transmission loss to carry the wireless high frequency signal to the service area several kilometers away. In addition, the RoF technique can implement the double frequency up-conversion by using the special RoF optical transmitter design. For example, a quadrupling frequency up-conversion can implement 60 GHz from a 15 GHz wireless signal such that the operation frequency of the electrical devices at the transmitting end can be dramatically decreased. Consequently, in addition such decreases in system complexity, the building cost of the entire system also decreases since low frequency devices with lower cost can be used to build the system.